The present invention relates to television cameras and in particular to the continuous depth of focus control of a television camera.
The generation and sales of video related advertising is a major industry within the field of television and one which generates millions of dollars for many companies whose products and services relate to the television and advertising industries. Thus, for example, suppliers of television recorders, cameras, switchers, editing systems, etc. are continually striving to provide new and better apparatus, techniques, aids, etc., for generating television advertising in the form of product commercials. Advertisers and television producers alike welcome any improvement in apparatus or techniques which decreases the time that it takes to produce a commercial, which simplifies the apparatus or procedure required to produce the commercial, or which enhances the dramatic affects of the commercial in its portrayal of a product to a viewer.
There are situations, particularly in television commercial production, when it is desirable to focus the viewer's attention on a person or product while under discussion. Thus, the person or product is kept in focus while the background, or a second object, is kept out of focus. At some point during the commercial presentation, it is desirable to bring the background or the second object into focus while maintaining the previously focussed person or product in focus.
Accordingly, the invention provides apparatus and method for controlling the depth of focus of a television camera as, for example, when generating television commercials in a studio environment. The scheme provides for focusing on a first object while keeping a second object or portion of the scene out of focus. To this end, in a television camera with automatic iris control, the variable gain of the camera is adjusted over a continuous range, which varies accordingly the video signal level. The auto iris control simultaneously detects the changing video signal level and, in keeping with its intended purpose, tries to maintain the preset video level. To do so, it changes over a continuous range the iris setting accordingly. The change of iris changes the depth of focus to bring into focus the second object. Thus, the depth of focus of the camera is varied over a continuous range by manipulating the variable gain control.
Accordingly it is an object of the invention to vary the depth of focus of a television camera by varying the gain of the camera.
It is another object to vary the depth of focus of a television camera via its automatic iris control, in response to a gain change.
It is a further object to perform a continuous change of depth of focus without changing lighting level or using special editing procedures.